Coccidians

Toxoplasma gondii. Tissue cyst in brain impression smear (Giemsa's stain, oil immersion). Numerous bradyzoites are seen within this spherical cyst. These cysts represent the chronic stage of infection, but when there is reactivation of infection in immunocompromised hosts (especially AIDS patients), the cysts will rupture and bradyzoites reinitiate active infection, causing toxoplasmic encephalitis.